1. Field of the Invention
The present invention relates to oil injection systems for two-stroke engines. More particularly, the present invention relates to an oil injection system having a pressure regulator for establishing an upper pressure limit in the oil line.
2. Description of the Related Art
Two-stroke engines require a fuel/oil mixture for operation, with the fuel component being ignited to drive one or more pistons, while the oil component lubricates the moving parts in the engine crankcase. Typically, the fuel and oil are pre-mixed externally of the engine, and the fuel/oil mixture is supplied to the engine cylinders from an external tank in which the fuel/oil mixture is stored. Recently, however, high-performance two-stroke engines have been developed which utilize injection systems in which the fuel and oil are each separately injected into the engine cylinders.
In one known oil injection system, oil is pumped by a diaphragm pump from an oil reservoir to a single oil injector, which injects the oil to a plurality of oil outlets for introduction into respective engine cylinders. The pump supplies oil in a great excess to that which is needed for introduction into the engine cylinders, necessitating a return line to communicate excess pumped oil from the single oil injector back to the oil reservoir, such that, in effect, the majority of the oil is continuously recirculated throughout the oil injection system. A disadvantage with this arrangement is that the single oil injector does not provide adequate metering of the pumped oil into each of the plurality of oil outlets, resulting in ineffective engine lubrication. A further disadvantage of this arrangement is the increased opportunity for leaks provided by the return line.
What is needed in the art is an oil injection system which provides adequate metering of oil to the engine, is simplified in overall design, includes simplified components, and is relatively simple and cost effective to manufacture.
The present invention provides an oil injection system for two-stroke engines, in which a pressure regulator located within an oil reservoir maintains pressure in a portion of the oil line and selectively returns oil from the oil line to the oil reservoir to prevent oil from exiting the reservoir at a higher than desired pressure. Because the pressure regulator is positioned within the oil reservoir, there is no need for a return line and the associated fittings.
Oil is pumped from the oil reservoir and is communicated to a valve, such as a solenoid valve, and is thereafter selectively conveyed to a plurality of oil injectors. The pressure regulator and the valve work together to meter the flow of oil to a plurality of oil injectors for injection into the engine cylinders. As a result of the superior oil metering capability provided by the pressure regulator and the solenoid valve of the current invention, an appropriately metered flow of pressurized oil is supplied to the oil injectors. Elimination of the oil return line, along with the location of the pressure regulator within the oil reservoir, reduces the risk of oil leaks occurring externally of the oil reservoir.
Positioning the pressure regulator within the oil reservoir advantageously simplifies the overall design of the oil injection system by eliminating a return line connecting the solenoid to the oil reservoir, as well as the fittings on the solenoid valve and on the oil reservoir which would be associated with the oil return line. The elimination of an oil return line additionally simplifies the structure of the solenoid valve by obviating the need for an outlet on the solenoid to allow flow to reach the oil return line.
In one form thereof, an oil injection system for a two-stroke engine is provided, including an oil reservoir containing a volume of oil therein; an oil pump disposed in the oil reservoir and operable to pump a measure of oil from the volume of oil through an oil line to the engine, the oil pump having a housing; and a pressure regulator disposed within the oil reservoir external of the pump housing and in fluid communication with the oil line, the pressure regulator selectively returning a portion of pumped oil to the volume of oil in the oil reservoir to prevent oil from exiting the reservoir at a pressure above a predefined pressure limit.
In another form thereof, an oil injection system for a two-stroke engine is provided, including an oil reservoir containing a volume of oil therein, the oil reservoir including an oil pump disposed within the oil reservoir and pumping oil from the volume of oil, and a pressure regulator disposed within the oil reservoir, the pressure regulator selectively returning a portion of pumped oil to the volume of oil in the oil reservoir to prevent oil from exiting the reservoir at a pressure above a predefined pressure limit, and a valve disposed externally of the oil reservoir and in fluid communication with the oil reservoir, the valve selectively operable between a first position in which the flow of pumped oil through the valve is blocked and a second position in which the flow of pumped oil through the valve is allowed.